ITFT_Computer Network
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Bandwidth is measured in bits per second and refers to the maximum rate of data transfer. Common units are kilobits per second (Kbps), megabits per second (Mbps), and gigabits per second (Gbps). To connect to the internet, a computer requires an internet service provider (ISP) account and a modem or network interface card. A local area network (LAN) connects computers within a home or building using Ethernet cables or WiFi, while a wide area network (WAN) connects locations over longer distances. The internet uses TCP/IP protocols to transmit data in packets across networks and IP addresses to identify devices.
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ITFT_Computer Network
- 2. Bandwidth • Data rate measured in bits (not bytes) per seconds • Kbps (Kilobits per seconds) • 125 chars/sec • Mbps (Megabits per seconds) • 1,250 chars/sec • Gbps (Gigabits per seconds) • 12,500 chars/sec
- 3. Connecting to the Internet • Requirement • A computer or PDA or cell phone • An account with an ISP (Internet Service Provider) • A modem (modulator/demodulator) for dial-up services or a NIC (Network Interface Card) for DSL/Cable services
- 5. Home Network (multiple machines) USB/Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch
- 6. Home Network (multiple machines) Ethernet Cable DSL/Cable Modem Wall Jack Hub/Switch/Rout
- 7. Connection Types • LAN • WLAN • Dial-up Services • Broadband Services • WAN
- 8. LAN (Local Area Network) • A network of computers that are in the same physical location, such as home or building • Usually connected using Ethernet • A standard on how computers communicate over a shared media (cable) http://en.wikipedia.org/wiki/Image:Ethernet_RJ45_connector_p1160054.jpghttp://en.wikipedia.org/wiki/Image:BNC_connector.jpg Old: BNC connector for coaxial cable New: RJ45 for twisted pair cable
- 9. LAN (Local Area Network) • Ethernet Standard • 10BaseT • 10Mbps (Mega bits per second) • 100BaseT • 100Mbps • 1000BaseT • 1000Mbps or 1Gbps • Correction from the book (pg. 10) • Why do we get faster connection at work or on campus than at home?
- 10. LAN (Local Area Network) • Question: Can 2 computers communicate by connecting each other using an Ethernet cable back-to-back?
- 11. WLAN (Wireless LAN) • Wi-Fi (Wireless Fidelity) • A wireless technology that connects computers without cables • Access Point (AP) • A device (base station) that connects wireless devices together • Usually connected to a wired-network • ESSID (Extended Service Set ID) • A “name” for the AP, eg. mobilenet • Hotspot • The area covered by wireless access points
- 12. WLAN (Wireless LAN) • Standard • 802.11b - 11Mbps • 802.11g - 54Mbps • 802.11a - 54Mbps • Security • WEP (Wired Equivalen Privacy) • WPA (Wi-Fi Protected Access) • To prevent wardriving 2.4G 5G
- 13. Dial-up Services • ISDN • Integrated Services Digital Network • 2 data channel (56K each) • 1 voice channel
- 14. Broadband Services • xDSL (Digital Subscriber Line) • A technology that provides digital data transmission over unused frequencies on traditional telephone lines • For example, ADSL (Asymmetric DSL): DL > UL • Speed • Downlink • 128Kbps - 4Mbps • Uplink • 64Kbps - 800Kbps • Need a DSL modem • Splitters are needed to separate the voice and data signal
- 15. Broadband Services • Cable • A technology that provides digital data transmission over cable TV infrastructure • Speed • Downlink • 128Kbps - 3~5Mbps • Uplink • 64Kbps - 128Kbps~1Mbps • Need a cable modem
- 16. Broadband Services • Satellite • A technology that provide digital data transmission over satellites • Speed • Downlink • 500Kbps - 1Mbps • Uplink • 50Kbps - 100Kbps • Need a satellite dish
- 17. WAN (Wide Area Network) • A LAN spans a large geographic area, such as connections between cities • Usually connected using leased line • T1 (1.5Mbps) • T3 (45Mbps) • OC3 (155Mbps) • OC12 (622Mbps) • OC48 (2.4Gbps) Fiber optic lines Telecommunication lines
- 18. Hub/Switch/Router • To connect multiple segments of networks into a larger one • Hub • A multiport repeater to enhance signal within the same LAN • Switch • Like hub but with intelligent • Better performance • Router • Forward packets from one LAN to another
- 19. Intranet vs. Internet • Intranet • A private network that is contained within an enterprise • Could be LANs and WANs • Internet • A public network of networks • Both are using TCP/IP
- 20. TCP/IP • A family of protocols that makes the Internet works • The Robustness Principle • “Be liberal in what you accept, and conservative in what you send” - Jon Postel
- 21. TCP/IP (cont) Application Layer Eg. WWW, FTP, IRC, Email, telnet, … Transport Layer Eg. TCP, UDP Network Layer Eg. IP Link Layer Eg. Ethernet, WiFi Physical Layer Eg. Ethernet Cable, fiber-optics Segments Packets Frames Bits Data
- 22. Packets • A small chunk of data transmitted over the Internet Alice The Internet Bob
- 23. VPN (Virtual Private Network) • A secure tunnel to a private network through a public network • Once established, local node appears to be a node in the private network in a secure manner • Correction from the book (pg. 11): • VPN does not mean using telephone line connection!!!
- 24. Host & IP Address • Correction from the book: “A host is a computer connected directly to the Internet” “You home computer is not a host” • Each host needs an IP address • IP address • A 32-bit number, arranged in 4 numbers seperated by “.” • Eg. 74.125.19.147
- 25. DNS (Domain Name System) • Domain name to IP address conversion • Eg. www.google.com → ??.???.??.?? • Domain name or IP address lookup • http://cqcounter.com/whois/
- 26. Top-level Domains • gTLDs (generic TLDs) • .com, .edu, .net, .org, .gov, .mil • .aero, .biz, .coop, .info, .museum, .name, .pro • ccTLDs (country code TLDs) • .au, .ca, .br, .de, .fi, .fr, .jp, .hk, .cn, .tw, .my, … • .us
- 27. Second-level Domains • Domains that are directly below a TLD • Eg. • ucr.edu • google.com • sony.co.jp • Must apply to a registrar for the appropriate TLD
- 28. How To Register A Domain Name? • Come up a new name • 2 name servers’ IP addresses • 1 administrative contact • 1 technical contact • Register the name to an Internet domain registrar • Eg. www.netsol.com, www.godaddy.com Used to be done via email or fax, now all web-based!